This invention relates to pressure jacket systems for securing a syringe in an injector head. More specifically, the invention relates to pressure jacket systems which allow front loading and removal of a syringe, and which hold the syringe securely to an injector head during injection procedures.
In the medical field, patients often are injected with fluids in procedures such as angiography. In such procedures, which require controlled injection of a large volume of fluid into a patient, a needle is used as a conduit for the fluid which is connected to the syringe by a connector tube. The syringe is mounted on a motorized injector having an injector head.
For long term compatibility with injectable fluids, syringes may be made of polypropylene with a certain minimum wall thickness. The thickness is critical as typical pressures of up to 1200 p.s.i. are used to inject the fluids into a patient. For safety and sanitary reasons, different disposable syringes are used or different fluids and different patients.
Pressure jackets are known in the art for enclosing and retaining syringes while in use. A pressure jacket serves to limit radial expansion of a syringe which may lead to bursting or to leaks of the pressurized fluid around the seals of the syringe plunger. Another function of a pressure jacket is to prevent forward motion of the syringe. For example, typically a force of 2000 pounds is required to restrain the forward motion of a 200 ml syringe with a cross-section of 1.7 in.2 at 1200 p.s.i.
Certain present pressure jackets are one piece designs, where the syringe is inserted into the jacket from the rear end of the jacket. An example of such a pressure jacket is found in U.S. Pat. No. 4,677,980, assigned to the common assignee of this application. The neck of the syringe protrudes from the front end of the pressure jacket for connection of fluid lines that lead to the patient. Because the diameter of the syringe neck is much smaller than that of the syringe barrel, it can withstand both radial and forward force.
However such an arrangement causes a problem when the syringe is removed from the pressure jacket. The neck of the syringe must pass through the present pressure jacket configurations. This requires the patient fluid path to be disconnected, which presents a potential biohazard and may result in spilling fluids onto the pressure jacket. Additionally, fluid spilled during loading and purging air from the syringe may get inside the pressure jacket and require cleaning.
Thus, a pressure jacket system is needed which permits a syringe to be front loaded onto an injector head and removed from the injector head without disconnecting the patient fluid path. Further, a pressure jacket system is needed which reduces the materials required for the manufacture of the syringe.